Osteoporosis is a systemic skeletal disease that affects millions of people worldwide. There are many possible etiologies for osteoporosis, including inherent variables like genetics and sex, and lifestyle variables like diet and exercise. Characterized by low bone mass and increased fracture risk, the disease places a burden on both the patients and the healthcare industry. Therefore, it is vital that research determine the mechanisms by which the risk factors affect BMD so that better diagnosis and treatment options may be developed. The purpose of this study was to examine the relationship between various osteoporosis risk factors and biochemical markers of osteogenic cell activity derived from bone-marrow MSCs. It was hypothesized postmenopausal white women, having the greatest risk for osteoporosis, would have elevated hydroxyproline and decreased ALP, indicative of greater bone resorption. Acetabular reamings were collected from 26 patients (15 males and 11 females) undergoing total hip arthroplasty at Boston Medical Center. MSCs from the reamings were plated and underwent osteoinduction into osteoblasts. The cells were then harvested and assayed for various indicators of cell growth and bone cell activity, such as DNA, ALP, and hydroxyproline. Our hypothesis was generally supported in that postmenopausal white women did have less ALP, an indicator of bone deposition, than premenopausal women and postmenopausal African American women. Additional findings and directions for future studies are further discussed in this paper.

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Articular cartilage is a smooth, white connective tissue that covers and protects the ends of long bones to allow for a smooth, frictionless surface on which to glide for easy movement. Once the tissue is damaged, articular cartilage lacks a direct blood supply, which results in a limited ability to repair itself. This study explores the effect of the growth factor BMP-13 on the chondroinduction of primary human bone marrow-derived mesenchymal stem cells. The results demonstrate the limited ability of BMP-13 to exert a strong chondroinductive effect on human bone marrow-derived MSCs. However, the results do indicate that BMP-13 has the ability to sustain chondroinduction to a certain extent for up to 18 days following initiation by 3 days of exposure to TGF-β3. Results are encouraging for future work that involves growth factor influence on MSCs in articular cartilage tissue engineering.

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The use of nanowires, nano and micro needles in biomedical applications has markedly increased in the past years, mainly due to attractive properties such as biocompatibility and simple fabrication. Specifically, these structures have shown promise in applications including cell separation, tumor cell capture, intracellular delivery, cell therapy, cancer treatment and as cell growth scaffolds. The work proposed here aims to study two platforms for different applications: a vertical magnetic nanowire array for mesenchymal stem cell differentiation and a micro needle platform for intracellular delivery. First, a thorough evaluation of the cytotoxicity of nanowires was done in order to understand how a biological system interacts with high aspect ratio structures. Nanowires were fabricated through pulsed electrodeposition and characterized by electron microscopy, vibrating sample magnetometry and energy dispersive X-ray spectroscopy. Studies of biocompatibility, cell death, cell membrane integrity, nanowire internalization and intracellular dissolution were all performed in order to characterize the cell response. Results showed a variable biocompatibility depending on nanowire concentration and incubation time, with cell death resulting from an apoptotic pathway arising after internalization. A vertical array of nanowires was then used as a scaffold for the differentiation of human mesenchymal stem cells. Using fluorescence and electron microscopy, the interactions between the dense array of nanowires and the cells were analyzed, as well as the biocompatibility of the array and its effects on cell differentiation. A magnetic field was additionally applied on the substrate to observe a possible differentiation. Stem cells grown on this scaffold showed a cytoskeleton and focal adhesion reorganization, and later expressed the osteogenic marker osteopontin. The application of a magnetic field counteracted this outcome. Lastly, a micro needle platform was fabricated through lithography and electrodeposition, characterized using the previously mentioned techniques and then evaluated as a vector for intracellular delivery. Fluorescence and electron microscopy imaging were first performed to assess the biocompatibility, cell spreading and the interface of the cells and the needles. Intracellular delivery of a fluorescent dye was achieved via inductive heating of the needles, with the results showing a dependency of delivery and cell survivability on the exposure time.

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Tendon injuries are a significant cause of morbidity in performance horses with superficial digital flexor tendon injury reported to represent up to 43% of overall Thoroughbred racehorse injuries. Natural repair is slow and results in inferior structural organization and biomechanical properties and, therefore, reinjury is common. The inability of tendon to regenerate after injury, or to heal with mechanical properties comparable to the original tissue, is likely attributable to low vascularity and cellularity of the tissue, low number of resident progenitor cells, and healing under weight-bearing conditions. Strategies to improve tendon healing have focused on enhancing the metabolic response of tenocytes, modulating the organization of the newly synthesized extracellular matrix, or administering progenitor cells to enhance repair. Significant research effort has been directed at the use of adult mesenchymal stem cells as a source of progenitor cells for equine tendon repair and recent clinical applications have utilized adult autologous stem cells derived either from adipose tissue or bone marrow aspirates. Isolation of a homogenous population of stem cells from bone marrow is time-consuming, and there is much variation in cell numbers, cell viability and growth rates among samples. Recently, a population of progenitor cells has been isolated from equine flexor tendons, thus providing an alternative source of progenitor cells from the target tissue for therapeutic intervention. The interaction between cells and the extracellular matrix (ECM) is an important factor in regulation of cell function. Proliferation, migration, differentiation and gene expression of many cell types are altered by adhesion to and interaction with matrix proteins and the extracellular environment. Tendon progenitor cells reside within a niche that comprises primarily parallel collagen fibers, and this niche plays an important role in regulating their function and differentiation. Culture conditions replicating this environment could be beneficial for both cell growth and matrix gene expression. The objectives of the study were to compare cell growth kinetics and biosynthetic capabilities of bone marrow mesenchymal stem cells (BMMSCs) and tendon derived progenitor cells (TPCs) cultured on commercially available bovine, highly purified bovine, porcine, and rattus collagen sources and standard tissue culture surfaces. We hypothesized that collagen type I matrix would preferentially support TPC proliferation and up regulate gene expression for collagens and organizational components of tendon and therefore provide a culture system and progenitor cell type with advantages over the current practice of BMMSC expansion on standard cell culture plastic surfaces. Cells were isolated from 6 young adult horses, expanded, and cultured on collagen-coated tissue culture plates, and no collagen control for 7 days. Samples were analyzed for cell number on days 4 and 7, and for mRNA expression of collagen type I, collagen type III, cartilage oligomeric matrix protein (COMP), and decorin on day 7. Glycosaminoglycan (GAG) synthesis was analyzed on day 7. Differences of cell number between collagen groups and cell type, and in gene expression and GAG synthesis between collagen groups and cell types, were evaluated by use of mixed-model repeated measures ANOVA. Pair-wise comparisons were made on significant differences identified with ANOVA using Tukey's post hoc test. Statistical significance was set at P<0.05. A statistical significant (P=0.05) increase in cell number for TPCs grown on rattus collagen versus control on day 4 was observed. No difference in GAG synthesis or expression of collagen type I, collagen type III, COMP or decorin mRNA was observed between collagen groups and non-collagen controls for either cell type on day 7. TPCs cultured on all collagen types yielded more cells than similarly cultured BMMSCs on day 4, but only porcine collagen was superior on day 7. TPCs synthesized more GAG than BMMSCs when cultured on control surfaces only. BMMSCs expressed more collagen type I mRNA when cultured on control, porcine and highly-purified collagen, and more collagen type III when cultured on control, porcine, highly-purified collagen, and rattus collagen, than TPCs. Tendon-progenitor cells expressed significantly more COMP when cultured on control and all collagen types, and decorin when cultured on porcine, highly purified bovine and bovine collagen when compared to BMMSCs. The results of this study revealed an advantage to culturing TPCs on randomly organized rattus collagen during the early growth phase. The beneficial effects of collagen-coated surfaces on cell proliferation is likely related to increased surface area for attachment and expansion provided by the random collagen matrix, and/or collagen-cell interactions. Tendon progenitor cells showed superior growth kinetics and expression of the matrix organizational components, COMP and decorin, than similarly cultured BMMSCs that expressed more collagen types III and I. TPCs synthesize more GAG compared to BMMSCs when cultured on plastic surfaces and there was no induction by collagen. Tendon progenitor cells should be considered as an alternative source of progenitor cells for injured equine tendons. Further in vitro studies characterizing factors that influence gene expression of both cell types is warranted. / Master of Science

Endotoxemia is a major cause of morbidity and mortality in horses. The presence of large amounts of circulating endotoxin inititates a number of cell signaling pathways leading to a systemic inflammatory response. Activation of these pathways causes the release of a number of pro- and anti-inflammatory mediators. An overwhelming release of these mediators leads to the development of clinical signs associated with endotoxemia. Treatment options are limited mostly to supportive care at this time. Mesenchymal stem cells (MSCs) have been shown to have anti-inflamamtory and immune modulatory effects that may have some benefit for the treatment of horses with endotoxemia. To evaluate the effect of equine MSCs on the response to endotoxin challenge, the study was performed on two different stem cell lines with peripheral blood mononuclear cells (PBMCs) used as controls. After stimulation with endotoxin, secretion of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and interferon gamma (IFN-γ) were determined by ELISA. The immunogenic properties of MSCs were assessed with a one-way mixed lymphocyte reaction. In addition, the ability of MSCs to alter production of cytokines from stimulated PBMCs was assessed. TNF-α was not produced by MSCs when compared to PBMCs (p = < 0.001). There was no significant difference between MSCs and PBMCs in the production of IL-6. IL-10 production was significantly different (p = <0.001) at 6 and 12 hours with MSCs producing more than PBMCs in one stem cell line only. MSCs did not stimulate proliferation of PBMCs. Co-incubation of MSCs with PBMCs decreased the production of TNF-α in both stem cell lines although it was not statistically significant (p = 0.4 and 0.9) at either time point. IL-6 secretion was suppressed at twelve hours with co-incubation. IL-10 production was increased with co-incubation in one stem cell line. MSCs secrete soluble factors that can alter PBMC cytokine production and they do not appear to be immunostimulatory. These findings have potential implication for treatment of equine inflammatory conditions. / Master of Science